Lipin 2/3 phosphatidic acid phosphatases maintain phospholipid homeostasis to regulate chylomicron synthesis

• Published in: The Journal of clinical investigation 2019-01, Vol.129 (1), p.281-295
• Main Authors: Zhang, Peixiang, Csaki, Lauren S, Ronquillo, Emilio, Baufeld, Lynn J, Lin, Jason Y, Gutierrez, Alexis, Dwyer, Jennifer R, Brindley, David N, Fong, Loren G, Tontonoz, Peter, Young, Stephen G, Reue, Karen
• Format: Article
• Language: English
• Subjects: Acid phosphatase; Animals; Apolipoprotein B-48 - genetics; Apolipoprotein B-48 - metabolism; Apolipoproteins; Biomedical research; Biosynthesis; Chylomicrons; Chylomicrons - biosynthesis; Chylomicrons - genetics; CTP:phosphocholine cytidylyltransferase; Endoplasmic reticulum; Enterocytes; Enterocytes - cytology; Enterocytes - metabolism; Enzymes; Fatty acids; Female; Gene expression; Genomes; Glycerol; Homeostasis; Lipid Droplets - metabolism; Lipids; Lipoproteins; Liver; Male; Mechanistic Target of Rapamycin Complex 1 - genetics; Mechanistic Target of Rapamycin Complex 1 - metabolism; Metabolism; Mice; Mice, Knockout; Musculoskeletal system; Phosphatase; Phosphatidate Phosphatase - genetics; Phosphatidate Phosphatase - metabolism; Phosphatidic acid; Phospholipid composition; Phospholipids; Phospholipids - genetics; Phospholipids - metabolism; Proteins; Rapamycin; Roles; Secretion; Small intestine; TOR protein; Triglycerides - biosynthesis; Triglycerides - genetics
• ISSN: 0021-9738; 1558-8238
• DOI: 10.1172/JCI122595

The lipin phosphatidic acid phosphatase (PAP) enzymes are required for triacylglycerol (TAG) synthesis from glycerol 3-phosphate in most mammalian tissues. The 3 lipin proteins (lipin 1, lipin 2, and lipin 3) each have PAP activity, but have distinct tissue distributions, with lipin 1 being the predominant PAP enzyme in many metabolic tissues. One exception is the small intestine, which is unique in expressing exclusively lipin 2 and lipin 3. TAG synthesis in small intestinal enterocytes utilizes 2-monoacylglycerol and does not require the PAP reaction, making the role of lipin proteins in enterocytes unclear. Enterocyte TAGs are stored transiently as cytosolic lipid droplets or incorporated into lipoproteins (chylomicrons) for secretion. We determined that lipin enzymes are critical for chylomicron biogenesis, through regulation of membrane phospholipid composition and association of apolipoprotein B48 with nascent chylomicron particles. Lipin 2/3 deficiency caused phosphatidic acid accumulation and mammalian target of rapamycin complex 1 (mTORC1) activation, which were associated with enhanced protein levels of a key phospholipid biosynthetic enzyme (CTP:phosphocholine cytidylyltransferase α) and altered membrane phospholipid composition. Impaired chylomicron synthesis in lipin 2/3 deficiency could be rescued by normalizing phospholipid synthesis levels. These data implicate lipin 2/3 as a control point for enterocyte phospholipid homeostasis and chylomicron biogenesis.